This invention relates to a method and an apparatus for conveying fiber-like material, particularly textile fiber tufts, entrained by an air stream from a main duct into at least two branch ducts. Such a pneumatic conveyance of fiber material is conventional in plants which prepare fiber material for processing in spinning mills.
In pneumatic tuft conveying systems the fiber tufts are, by means of a conveying medium such as an air stream, driven through a duct system and admitted to one or more machines which are connected to the common duct system and which may be, for example, openers, cleaners or conveyors or may be carding machines equipped with feed chutes.
It has been found that the degree of the moisture content of fiber tufts or that of the pneumatic system affects not only the charging of the machines such as the charging of feed chutes of carding machines, but also affects the conveyance of the fiber tufts in the ducts. The fiber tufts conveyed in the duct do not behave uniformly. It is a frequent occurrence that, for example, at locations of branch-offs (hereafter "branching zones"), bends or other walls of the conveying ducts, fiber tuft accumulations occur which obstruct the ducts, so that not only the conveyance in the duct is hindered, but also a uniform supply or further processing of the tufts by the successive machine or the charging, for example, of a feed chute of a carding machine are adversely affected. In particular, the risks are high that a uniform deposition of fiber material in the feed chutes of cards is adversely affected as early as the fiber tuft delivery involved with an earlier opening or cleaning process which thus has, during further processing, negative influence on maintaining the number value of a sliver or yarn made of the fiber material.
The occurrence of undesired fiber agglomerations, particularly of chemical fibers in pneumatic tuft delivering systems is most frequently caused by the generation of electrostatic charges. Such charges may be generated by friction resulting from a turbulence in the conveying air stream, by friction between the fiber tufts and the air stream as the processing machine receives the fiber tufts from the delivery system or because of friction between the fiber tufts themselves. Since the fiber tufts move freely in the conveying air stream, the electrostatic charge is not removed and thus remains preserved until the fiber tufts contact an appropriate material which conducts electrostatic charges. In particular, agglomerations of fiber tufts have been observed in relatively dry transport air. Even an excessively high moisture content of the transporting air or the fiber material itself leads to an agglomeration of the fiber tufts which causes not only malfunctions in the pneumatic delivery system but also adversely affects the quality of the product made of the fiber. Since brightening agents applied to the fibers are frequently highly hydroscopic, an adherence of the fiber tufts to one another and to the walls of the ducts because of excessive air humidity is very likely, leading rapidly to malfunctions in the pneumatic air delivery system.
In case of a T-branch, for example, where a main duct is divided into two branch ducts, at the location on the duct walls on which the fiber tufts entrained by the air stream impinge, undesired fiber tuft accumulations occur and thus, fiber material builds up in substantial clumps at those locations. The intermittent release of such clumps causes the fiber tuft material to be admitted in an irregular flow into the one or the other branch conduit and obstructs the conduit. Such occurrences cause significant operational disturbances.